Process and composition for phosphatizing metals



United States Patent 3,197,345 PRQ CESS AND CUMPGSHTEON FGR PHUSPHATIZENG h ETALS William J. Vullo, Tonawanda, N.Y., and Donald H.

(Jamphell, Niagara-on-the-Lahe, Gntario, Canada, assignors to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Qrigiuai application Mar. 21, 1960, Ser. No. 16,125. Divided and this application June 20, 1963, Ser. No. 289,444

20 Claims. (Cl. 148-615) This invention relates to a process and composition for phosphatizing metals. More particularly, this invention relates to an improved, substantially water-free phosphatizing liquid, and to the process for applying phosphate coatings to metal surfaces with such a phosphatizing liquid.

This application is a division of our copending application Serial No. 16,125, filed March 21, 1960.

Phosphate coatings are applied to metal surfaces to prevent oxidation of the metal and to condition the metal surfaces for applying paint finishes. Metal surfaces should be free from rust, oil and other extraneoussubstances in order to obtain a satisfactory phosphate coating. Therefore the metal is cleaned in inorganic solutions such as hot alkaline solutions, in organic solutions such as chlorinated hydrocarbons, or othervrise cleaned prior to phosphatizing. In one method of cleaning, metal articles which may be coated with a film of rust-preventative oil, called slashing oil, are first subjected to a degreasing operation in which oil and extraneous materials are removed by contacting the metal with a chlorinated hydrocarbon, such as trichlorethylene, perchloroethylene, and trichloroethane in liquid and/ or vapor form.

Several methods for applying phosphate coatings to metal surfaces have been previously employed. In one method, which is referred to as the aqueous method, the metal is cleaned in a hot alkaline solut on, rinsed, immersed in a hot aqueous phosphatizing solution, then rinsed, immersed in chromic acid, and dried. Such a process has the disadvantage of requiring a large number of expensive operating steps. In addition, sludge rapidly builds up in the aqueous phosphatizing solution, thereby inhibiting the effectiveness of the phosphatizing bath. In another process, which is referred to as the dry process, the degreased metal is immersed in a solution of phos phoric acid and an organic solvent, such as acetone, carbon tetrachloride, lower alcohols, and the like. Phosphatizing solutions such as these have relatively low boiling points, and as a result, large proportions of the solvent are lost by vaporization. in addition, these phosphatizing baths have relatively low flash points. In an other dry process the phosphatizing bath consists of trichloroethylene, phosphoric acid and an alkyl acid phosphate. In phosphatizing baths of this type, the alkyl acid phosphate solvent may react with the metal, thereby introducing potentially harmful substances on the metal surface. Furthermore, the free phosphoric acid content of the bath cannot be readily determined by simple titration procedures because of the interference of the alkyl acid phosphate. In addition, rinsing of the coated panel is necessary prior to painting.

It is an object of this invention to provide an improved composition for phosphatizing metals.

It is another object of this invention to provide an improved process for phosphatizing metals.

Still another object of this invention is to provide an improved phosphatizing composition whch is relatively nonilammable and which is substantially water-free.

A further object of the invention is to provide an improved phosphatizing composition containing a novel inice hibitor which enhances the formation of hard, uniform, impervious microcrystalline phosphate coatings on metal surfaces.

It is a further object of the invention to provide a novel phosphatizing composition which contains organic compounds which are substantially non-reactive with metals.

These and other objects of the invention will be apparent from the following detailed description.

It has now been discovered that thin, uniform, hard,

impervious, microcrystalline phosphate coatings are readily formed on degreased metal surfaces when the metal surfaces are contacted with a solution of chlorinated hydrocarbon, an organonitro compound, phosphoric acid and a solvent capable of dissolving phosphoric acid in the chlorinated hydrocarbon. In addition, metals coated with such a solution can be readily painted to yield a finish having improved resistance to corrosion by salt spray and water. When the organonitro compound is omitted from the phosphatizing bath, and phosphatizing is effected under conditions described below, the resulting phosphate coatings are porous, macrocrystalline, thick and otherwise unsatisfactory.

Any metal of the class capable of reacting with phosphon'c acid to form the corresponding metal phosphate, such as iron, aluminum, zinc, magnesium, cadmium, al loys containing these metals and the like may be treated in accordance with the instant novel process.

Prior to phosphatizing, the metal is cleaned by any suitable means such as by employing chlorinated hydrocarbon to remove oil and extraneous material. The chlorinated hydrocarbon is preferably maintained at or near the boiling point, and the metal to be cleaned is contacted with the liquid phase and/or the vapor phase. The metal article, which has been cleaned in the chlorinated hydrocarbon, or otherwise cleaned, is then contacted with aphosphatizing solution containing the following ingredients in the following proportions.

Percentage Preferred Component by weight percentage by weight Chlorinated Hydrocarbon 65-98 -97 Phosphoric Acid 0. 1-6 0. 6-2 Solvent 1. 5-35 3-20 Organonitro Compound 0. 016 0.3-2

It is preferred to employ a chlorinated hydrocarbon containing a stabilizing composition, but unstabilized chlorinated hydrocarbons can be employed if desired. Typical examples'of stabilizers which may be suitable include olefins, as disclosed in United States Patents Nos. 1,904,450 and 2,435,312; acetylenic compounds, as disclosed in United States Patents Nos. 2,775,624 and 2,803,676; hydrocarbons, as disclosed in United States Patents Nos. 1,816,895 and 1,858,022; phenols, as disclosed in United States Patents Nos. 2,008,680 and 2,155,723; alcohols, as disclosed in United States Patents Nos. 2,775,624 and 2,887,516; esters, as disclosed in United States Patent No. 2,371,646; ethers and epoxides, as disclosed in United States Patent No. 2,371,645; heterocycles containing N and O or S in ring, as disclosed in United States Patent No. 2,517,893; aldehydes, as disclosed in United States Patent 1,151,255; mercaptans, as disclosed in United States Patent No. 1,917,073; alkyl cyanamides, as disclosed in United States Patent No.

2,043,257; alkyl thioureas, as disclosed in United States Patent No. 2,043,258; alkyl amines, as disclosed in United States Patent No. 2,096,735; aryl amines, as disclosed in United States Patent No. 2,094,367; alkyl isocyanates, as disclosed in United States Patent No. 2,108,390; guanidines, as disclosed in United States Patent No. 2,125,381; diols, as disclosed in United States Patent No. 2,355,319; oximes, as disclosed in United States Patent No. 2,- 371,647; ketones, as disclosed in United States Patent No. 2,376,075; nitriles, as disclosed in United States Patent No. 2,422,556; amides, as disclosed in United States Patent No. 2,423,343; nitrates, as disclosed in United States Patent No. 2,436,772; thiophenes, as disclose in United States Patent No. 2,440,100; pyrroles, as disclosed in United States Patent No. 2,492,048; nitroalkanes, as disclosed in United States Patent No. 2,- 567,621; sulfones, as disclosed in United States Patent No. 2,742,509; azines, as disclosed in United States Patent No. 2,878,297; aryl stibines, as disclosed in United States Patent No. 2,917,554; sulfoxides, as disclosed in United States Patent No. 2,919,295; and mixtures thereof. This list of stabilizers is intended to be illustrative and is not an exhaustive list.

Some of the mixtures of the stabilizers may have a synergistic effect under certain phosphatizing conditions as evidenced by the elimination or inhibition of reaction products, oxidation products, hydrolysis products, polymerization products, decomposition products and the like.

Since the chlorinated hydrocarbons are relatively nonflammable and have a relatively high flash point compared to alcohols, it is preferred to use the highest proportion of chlorinated hydrocarbon in the bath consistent with obtaining a smooth, uniformphosphate coating on the metal.

it is preferred to employ highly concentrated orthophosphoric acid such as the eightyfive percent phosphoric acid of commerce, but more dilute or more concentrated acid solutions can be employed if desired. Regardless of the acid concentration initially employed, substantially all of the water is ultimately distilled from'the phosphatizing bath as the phosphatizing treatment progresses. The phosphatizing proportion of phosphoric acid referred to in the description and claims may be between about 0.1 and about six percent, and preferably between about 0.6 and about two percent by weight of the phosphatizing solution.

Since concentrated phosphoric acid is insoluble in chlorinated hydrocarbons, it is necessary to employ a solvent in the above defined proportions to dissolve the phosphoric acid in the chlorinated hydrocarbon liquid. Any aliphatic or alicyclic alcohol capable of dissolving phosphoric acid in the chlorinated hydrocarbon solution may be employed. Typical examples of suitable alcohols include the alcohols which contain between one and about eighteen carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tertiary butanol, tertiary amyl alcohol, octanol, decyl alcohol, lauryl alcohol, stearyl alcohol, cyclohexyl alcohol, and mixtures thereof. Since the solubility of phosphoric acid is less in the higher alcohols than in the lower alcohols, it is preferred to employ an alcohol having less than about ten carbon atoms, and more preferably between one and about six carbon atoms.

It has been noted that normal butyl alcohol has several advantages when compared to other alcohols. Firstly, when trichloroethylene is employed as the chlorinated hydrocarbon, a butanol-trichloroethylene azeotrope forms which boils at a temperature 86.65 degrees centigrade) slightly below the boiling point of trichloroethylene (about 87 degrees centigrade). ,The azeotropes formed with many other alcohols boil at somewhat lower temperatures. Secondly, normal butanol dissolves a higher proportion of phosphoric acid than other alcohols, thus requiring less alcohol solvent. Thirdly, the normal butyl alcohol-trichloroethylene azeotrope contains about 2.5 percent of normal butyl alcohol, thus effecting a concentration of the alcohol in the phosphatizing solution, when the initial concentration of alcohol in the phosphatizing solution is greater than about 2.5 percent by weight. Thus, depiction of the alcohol in the pot, which may cause the formation of two liquid phases, due to the insolubility of phosphoric acid in the chlorinated hydrocarbon, is avoided and the need for close control of the concentration of normal butyl alcohol in the pot is greatly reduced.

Other solvents capable of dissolving phosphoric acid in chlorinated hydrocarbons may be used in place of or with the alcohol solvent. Such solvents include halogenated alcohols such as 2-chloroethanol, polyols such as -ethyl-2-butyl-propanediol-l,3, alkyl acetates such as ethyl acetate, amyl acetate and the like, amides such as N,N-dirnethyl formamide and dimethyl acetamide, dioxane, monoethers of polyalkylene oxide glycols such as the cellosolves and carbitols, lretones such as acetone and methyl ethyl ketone, and dialkyl sulfoxides such as dimethyl sulfoxide. Solvents for H 1 0, which are neutral, e.g., those which in aqueous solution are neutral to litmus paper, such as those recited above, have been found to be useful in this process.

It is important to add an inhibiting proportion of a polar organonitro compound to the phosphatizing solution in the above described proportions in order to obtain the desired properties in the resulting phosphate coating. The organonitro compounds which are effective are those compounds which may be referred to as nitrated organic compounds containing the nitro group. Either aliphatic nitrocompounds, aromatic nitrocompounds or mixtures thereof may be employed. Typical examples of suitable aliphatic nitrocompounds include nitromethane, nitrourea, nitroguanidine, nitroethane, and mixtures thereof. Typical examples of aromatic nitrocompounds include nitrobcnzene, dinitrobenzene and mixtures thereof. Organonitrocompounds substituted with chlorine, hydroxyl and/ or carboxyl groups may also be employed. For example, 1-chloro-4-nitrobenzene, p-nitrophenol, m-, o-, or p-nitrobenzoic acid, picric acid and the like are suitable inhibiting compounds. However, any suitable organonitro compound capable of enhancing the formation of hard, uniform phosphate coatings may be employed. Nitrobenzene and dinitrobenzene appear to be very effective in this respect. The inhibiting proport1on of organo nitro compound referred to in the description and claims may be between about 0.01 and about six percent and preferably'between about 0.3 and about two percent by weight of the phosphatizing solution.

it has been found that when an organonitro compound is employed as a component of the phosphatizmg solution in the proportions set forth above, the resulting phosphate coating is smooth, uniform, hard and microcrystalline. The phosphate coating in such a case 1s generally of the order of between about twenty-five and about two hundred milligrams per square foot. However, when the organonitro inhibitor is omitted from the phosphatizing solution, the resulting phosphate coatrugs are heavy, porous, uneven and macrocrystalline, especially when the concentrationof phosphoric acid in the phosphatizing bath is in excess of about 0.6 percent by weight. In the latter case, without the inhibitor, the phosphate coating generally weighs in excess of about three hundred milligrams per square foot and is occasionally over one gram per square foot. The porous nature of the phosphate coating obtained without such an inhibitor probably accounts for the poor paint-bonding properties which result. It has also been discovered that the Weight of the phosphate coating is, under a given set of conditions, inversely proportional to the concentration of organonitro compound in the phosphatizing solution. This result is entirely unexpected in view of the prior art teaching of the use of nitrobenzene and other nitro compounds to accelerate the formation of phosphate coatings in aqueous phosphatizing baths.

In the process for applying the phosphate coating, the degreased metal is contacted with the novel phosphatizing solution described above for a period of time up to about thirty minutes and preferably between about 0.5 and about fifteen minutes. The bath is maintained at a temperature between about twenty de rees centigrade and the boiling point of the solution, and preferably between about fifty-five and about seventy degrees centigrade, the higher temperature usually being employed when the shorter contact times are employed.

If desired, the phosphatized metal, after removal from the bath, may be returned to the chlorinated hydrocarbon degreasing solution for a final rinse to remove phosphatizing solution, but this step is often not necessary since the phosphatized metal is generally substantially dry when removed from the phosphatizing bath. The phosphatized metal article, with or without rinsing, as the case may be, can be stored or used as is. If desired, the phosphatized metal article may be subjected to further treatment such as painting, lubricating and the like. The phosphate-coated metals resist corrosion and retain paint finishes as well as or better than metals phosphatized by conventional aqueous or dry processes.

It has been found that the effectiveness of the novel phosphatizing solution is enhanced on start-up by admixing the solution with a small proportion of powdered iron or other metal of the class being treated (i.e., between about 0.01 and about 0.1 percent by weight of solution), heating the resulting slurry to between about fifty-five degrees centigrade and about the boiling point for between about ten and about fifty minutes, and then separating suspended solids from the slurry by filtration or the like, prior to employing the solution in the phosphatizing of metal articles. However, when a novel phosphatizing solution has not been so treated with iron powder, occasionally the first one or two articles coated with the untreated phosphatizing solution have phosphate coatings that are not as satisfactory as the coatings of the metal articles subsequently produced from the phosphate solution. Prior treatment of the phosphatizing solution with iron powder as described above, results in the formation of superior phosphate coatings on all of the metal articles treated.

The following examples are presented to define the invention more fully without any intention of being limited thereby. All parts and percentages are by weight unless otherwise specified.

Example 1 milliliters of nitrobenzene were admixed with the result,

ing solution in a one liter beaker. The composition of the phosphatizing solution was as follows: I

Component: Percent by weight Trichloroethylene 91.9 Normal butyl alcohol V 6.5 Phosphoric acid (85%) 1.2 Nitrobenzene 0.4

Four bare steel panels, twenty-four gauge, three by five inches, were degreased in trichloroethylene vapors, and were consecutively immersed in the aforesaid phosphatizing solution for a period of about ten minutes each at sixty-five degrees centigrade. Each of the panels, after removal from the phosphatizing solution, although it was dry, was rinsed in trichloroethylene vapors for about fifteen seconds. The panels were then painted by rolling with a white baking enamel, baked for thirty minutes at one hundred and sixty degrees Centigrade, and aged for about twenty-four hours.

Two of the panels were subjected to a salt fog spray test, employing the salt fog spray technique as described in ASTM designation No. B11754T. In this test each panel was scored vertically with a sharp knife, and subjected to an atomized fog of a five percent aqueous sodium chloride solution at a temperature of about ninetyfive degrees fahrenheit for about ninety-four hours. The panels were then rinsed in water and wiped dry. A one inch wide stainless steel spatula was then scraped along the score mark. The width of area of paint removed in scraping was about one millimeter and less than about one millimeter for the .two panels, respectively.

For purposes of comparison, two additional bare steel panels were degreased in trichloroethylene vapors, and then without phosphatizing, were painted with white baking enamel in the same manner as the other panels. non-phosphatized painted panels were subjected to the salt fog spray test at the same time as the two phosphatized painted panels. The width of area of paint removed in scraping the non-phosphatized painted panels was 7.7 and fifteen millimeters, respectively, thus demonstrating that the panels phosphatized in accordance with the instant novel process have superior paint bonding properties under highly corrosive conditions.

The four painted panels (two of which were phosphatized and two of which were not), after completion of the salt fog spray test, were subjected to a tape test wherein a V was scribed through the paint coating to the bare metal. The legs of the V were about one inch long and the opening of the V was about one-half an inch wide. Cellophane adhesive tape was rubbed and pressed into intimate contact with the coating and covered the V such that a three inch tail of tape was left loose above the apex of the V. The tape was then pulled back suddenly in a manner such that it was removed at an angle of about one hundred and eighty degrees to itself. The paint removed around the V determined the adhesion of the paint in accordance with the following rating system? 1peeling beyond lines and tape 2peeling beyond lines, but under tape 3peeling within lines, entire area 4-peel-ing within lines, greater than one-half the area 5-peeling within lines, greater than one-quarter the area 6 peeling within lines less than one-quarter the area 7 jagged peeling along cuts to one-eighth inch 8-smooth peeling along cuts to one-eighth inch 9trac'e of peeling 10no peeling The two phosphatized painted panels had a tape rating of nine and ten respectively, while the non-phosphatized painted panels both had a rating 2, thus further demonstrating the superior paint bonding properties of the novel phosphatized coating.

Two of the phosphat-ized panels were painted in the same manner as the other panels and after curing were subjected to a water immersion test by immersing them in distilled water-at seventy-two degrees centigr ade, and then rated in accordance with ASTM No. D714-54T. After sixteen hours the panels had a rating of ten (no trace of blisters) and after eighty hours thepanels had a rating of nine-few. t 1

Example 2 Perchloroethylene (nine hundred and forty-four grams), isopropyl alcohol (94.8 grams), and eighty-five percent phosphoric acid (twelve grams) were admixed with about two hundred milligrams of iron powder in a The p one lifer beaker, heated to sixty degrees centigrade for thirty minutes and then filtered through glass wool. Nitrobenzene (3.6 grams) was admixed with the clarified filtrate, and 3.9 grams of isopropyl alcohol and seventysix grams of perchloroethylene were added to restore the volume of the solution to its original seven hundred milliliters. The composition of the resulting phosphatizing solution was approximately as follows:

Component: Proportion, percent Perchloroethylene Phosphoric acid (85%) 1.1 Isopropyl alcohol 8.6

Nitrobenzene .3

Three bare steel panels were degreased, phosphate coated in this phosphatizing solution and rinsed in accordance with the procedure of Example 1.

One of the phosphatized panels was treated to determine the weight of phosphate coating by stripping the phosphate coating in an alkaline solution of sodium cyanide as described in Industrial Finishings, volume 9, page 878, 1957. The weight of phosphate coating was found to be forty-seven mg./ft.

The other two phosphate coated panels were painted as in Example 1. A fourth panel was degre-ased, and without phosphatizing, was painted in the same manner. The three painted panels were subjected to the salt fog spray test of Example 1 for seventy hours. The width of thet area of paint removed by scraping of the two phosphatized painted panels was less than one and about.1.5 millimeters respectively, and for the non-phosphatized painted panel was about six millimeters.

Example 3 1,1,l-trichloroethane (eight hundred and twenty-three grams), eighty-five percent phosphoric acid (twelve grams,) and isopropyl alcohol (63.2 grams) were admixed with about two hundred milligrams of iron powder, heated for about thirty minutes at sixty degrees centigrade and then filtered through glass wool. Nitrobenzene (3.6 grams) was admixed with the resulting clarified filtrate. The composition of the resulting solution was as follows:

Component: Proportion, percent 1,1,1-trichloroethane 91.3 85% phosphoric acid 1.1 Isopropyl alcohol 7.0 Nitrobenzene 0.4

Three baresteel panels were immersed in the solution, one by one, for fifteen minutes at sixty degree Centigrade, and then rinsed in trichloroethylene. Stripping of one of the coated panels, as in Example 2, showed a phosphate coating weight of 47.5 mg./ft. Two of the coated panels, after painting as in Example 1 were subjected to the salt fog spray test along with a non-phosphatized painted panel as in Example 1. The width of the area of paint removed by scraping the two phosphatized painted panels was less than one and about 1.5 millimeters respectively, and for the non-phosphatized painted panel was about six millimeters.

Example 4 The procedure of Example 1 was repeated employing cyclohexyl alcohol as the solvent. The phosphatizing solution had the following composition:

Component: Proportion, percent Trichloroethylene 90.6 85% phosphoric acid 1.2 Cyclohexyl alcohol 7.8 Nitrobenzene 0.4

Two bare steel panels were coated in this solution, then painted and subjected to the salt fog spray test. The width of area of paint removed by scraping was about one millimeter in each case. Two non-phosphatized, painted panels tested in the same manner had a width of paint removed of 7.7 and fifteen millimeters respectively.

Example 5 A phosphatizing solution having the following approximate composition:

Component: Proportion, percent Trichloroethylene 92.9 Normal butyl alcohol 5.6 phosphoric acid 1.1 Nitrobenzene 0.4

which had been previously used for phosphatizing, was used to phosphatize two degreased bare steel'panels by immersing each of the panels in the solution at sixty-four degrees cent-igrade for one minute. After a trichloroethylene rinse, the panels, were painted by dipping in a trichloroethylene-base white baking enamel, using a Fischer-Payne dip coater to remove the panels from the paint at a uniform rate. The painted panels were then baked for thirty minutes at about one hundred and fortyfive degrees cent-igrade and aged over forty-eight hours. An X was scored across one surface of'each of the panels and each was subjected to the salt fog spray test for one hundred and sixteen hours along with two non-phosphatized painted panels scored in the same manner. The panels were then removed from the spray, rinsed in water and gently wiped dry. ()ne of the non-phosphatized painted panels was completed rusted over the entire surface, and the second one was rusted over between oneeighth and one-quarter of the surface. The paint was loose and badly blistered on both panels. In contrast, both of the phosphatized painted panels were substan tially free from rust except along the score marks, and the paint was firm, thus demonstrating the superior paint bonding properties of the novel phosphate coating.

Example 6 Component Proportion,

grams Weight Percent Triehloroethylene 85% Phosphoric Acid Isopropyl Alcohol N itrobenzene The bath, without prior iron powder treatment, was used to phosphatize several panels before carrying out this example. Three degreased bare steel panels were immersed in the bath consecutively for ten minutes at sixtyfive degrees centigrade, and then, without a trichloroethylene rinse, were painted as in Example 1. Two of the panels were subjected to salt fog spray test for one hundred and thirteen hours. The width of paint area removed by scraping was less than one millimeter in each case, and the tape test showed a rating of nine in each case. A nonphosphatized painted panel, after subjecting to the same salt fog spray test had a width of paint area removed by scraping of thirty-seven millimeters, and a tape test rating of two.

The third phosphatized painted panel was subjected to the water immersion test, as in Example 1, for sixteen hours, and attained a rating of nine-medium.

Example 7 Tr'ichloroethylene (eleven hundred and fifty grams), eighty-five percent phosphoric acid (fourteen grams), and normal butyl alcohol (sixty-five grams) were admixed with powdered iron (one hundred milligrams) for thirty minutes at sixty degrees centigrade, and then filtered through glass wool. Dinitrobenzene (4.82 grams) was added-to the resulting clarified filtrate. Four degreased bare steel panels were consecutively immersed in the bath for five minutes each, at a temperature of sixty-five degrees centigrade. Three of the panels were painted as in Example 1. Two of the painted panels were subjected to the salt fog spray test of Example 1 for seventy-two hours. The width of the area of paint scraped from these panels was one and two millimeters respectively while the corresponding width of non-phosphatized painted panel subjected to the same test was 14.6 millimeters.

One of the phosphatitzed painted panels was subjected to the water immersion test of Example 1 and had a rating of ten after sixteen hours. When a non-phosphatized painted panel was subjected to the same test, the paint was loose and blistered and had a rating of less than one.

The non-painted phosphatized panel, when stripped of phosphate coating as in Example 2, had a coating weight of about forty mg./ft. For purposes of comparison, when dinitrobenzene was omitted'from the solution prepared as described above, and panels were phosphatized therein, the resulting phosphate coating, as determined by the stripping test of Example 2 was seven hundred and ninety-five mg./ft.

Example 8 A phosphatizing bath was prepared by admixing the following ingredients in the following proportions:

A bare steel panel of the type employed in Example 1 was immersed in the bath for five minutes at a temperature of sixty-five degrees centigrade. The panel was sticky and the phosphate coating on the panel was blistered extensively. The weight of the phosphate coating, as determined in accordance with the procedure of Example 2 was one thousand eight hundred and sixty-five mg./ft.

The phosphatizing bath was then admixed with two hundred milligrams of powdered iron, the resulting slurry was heated to a temperature of seventy degrees centigrade for about thirty minutes, and then filtered through glass wool. Another steel panel was immersed in the resulting clarified solution for five minutes at sixty degrees centigrade. The phosphate coating was slightly tacky and weighed four hundred and eight milligrams per square foot as determined by the procedure of Example 2.

Nitrobenzene was added to the phosphatizing bath to produce a bath having the following composition:

Component: Proportion by weight, percent Trichloroethylene .65.3 85% phosphoric acid 1.1 Ethyl acetate 32.9 Nitrobenzene 0.7

Another steel panel was immersed in the latter phosphatizing solution for five minutes at a temperature of sixty degrees centigrade.

The resulting phosphate coating weighed eighty-four mg./ft. as determined in accordance with the procedure of Example 2.

Example 9 The procedure of Example 8 was repeated, employing N,N-dimethylformamide instead of ethyl acetate as the solvent for phosphoric acid. It was found that the phosphate coating obtained from such a phosphatizing bath without prior iron treatment and without the addition of nitrobenzene were almost three times as heavy as the coatings obtained when the bath had been previously treated with iron powder and a small proportion of nitrobenzene had been added to the bath.

Examples 10-16 Trichloroethylene (5210 grams), normal butyl alcohol (322 grams) and eighty-five percent phosphoric acid 10 Component: Percent Trichloroethylene 92.5 Normal butanol 6.6 Phosphoric acid 0.9

This solution which was designated as Solution A, was heated to sixty-five degrees centigrade, and a bare steel panel of the type employed in Example 1 was immersed in the solution for about five minutes, and then rinsed in trichloroethylene vapors. The phosphate coatings of this panel were thick, blistered, non-uniform, and had a grey color. The coating weight on the panel as determined in accordance with the procedure of Example 2 is set forth in the following table as Example 10.

Seven hundred and sixty milliliters of Solution A were admixed with 4.82 grams of 1-chloro-4-nitrobenzene in a one liter beaker. The resulting solution was designated as Solution B. A bare steel panel was immersed in this solution for five minutes at sixty-five degrees centigrade, and rinsed in trichloroethylene vapors. The coating weight on the panel was determined by the procedure of Example 2, and is set forth in the following table as EX- ample 11.

Four additional seven hundred and sixty milliliter portions of Solution A were admixed with 4.82 grams of a different additive,-i.e., p-nitrophenol, p nitrobenzoic acid, nitromethane, and dibntylphthalate, respectively. The resulting solutions were designated Solutions C, D, E and F, respectively, and the coating weight on the panels treated with these solution are set forth in the table as Examples 12, 13, 14 and 15, respectively.

Solution F was admixed with 4.82 grams of nitrobenzene (the resulting solution being designated as Solution G), and a panel was coated in this solution. The weight of the resulting phosphate coating is set forth in the table as Example 16.

Coating Example Solution Additive Weight,

Non

e 1-0h1oro-4-nitrobenzene p-Nitrophenol p-Nitrobenzoic a Nitromethane Dibutylphthalate Dibutylphthalate and Nitrobenzene meadow It can be seen from these tests that the weights of phos- I phate coating produced by phosphatizing solutions containing organonitro compounds (Solutions B, C, D, E and G) were substantially less than those which did not contain the novel inhibitor (Solutions A and F). In addition the coatings obtained with Solutions B, C, D, E and G were uniform, thin, impervious grey-blue coatings.

The words contacted and contacting, as usedv 1 1 suitable for phosphatizing metal consisting essentially of a chlorinated hydrocarbon containing a minor proportion of an organic solvent'capable of dissolving orthophosphoric acid in the chlorinated hydrocarbon, a phosphatizing proportion of orthophosphoric acid, and an inhibiting proportion of at least 0.01 percent by weight of a nitrated organic compound containing the nitro group, capable of inhibiting the formation of a heavy phosphate coating while enhancing the formation of a hard, uniformly thin phosphate coating.

2..A substantially water-free composition of matter suitable for phosphatizing metals consisting essentially of between about 65 and 98 percent by weight of a chlorinated hydrocarbon, between about 1.5 and about 25 percent by weight of an organic solvent capable of dissolving orthophosphoric acid in the chlorinated hydrocarbon, between about 0.1 and about 6 percent by weight of orthophosphoric acid, and between 0.01 and about'6 percent by weight of a nitrated organic compound containing the nitro group, capable of inhibiting the formation of a heavy phosphate coating while enhancing the formation of hard, uniformly thin phosphate coating.

3. The composition as claimed in claim 2 wherein the chlorinated hydrocarbon is trichloroethylene.

4. The composition as claimed in claim 2 wherein the chlorinated hydrocarbon is perchloroethylene.

5. The composition as claimed in claim 2 wherein the nitrated organic compound containing the nitro group is an aromatic nitro compound.

6. The composition as claimed in claim 2 wherein the nitrated organic compound containing the nitro group is nitrobenzene.

7. The composition as claimed in claim 2 wherein the solvent is an alcohol.

8. The composition as claimed in claim 7 wherein the alcohol contains between about one and about six carbon atoms.

9. A substantially water-free composition of matter suitable for phosphatizing metals consisting essentially of between about 85 and about 97 percent by weight of a chlorinated hydrocarbon, between about 3 and about percent by weight of an alcohol, between about 0.6 and about 2 percent by weight of orthophosphoric acid, and between about 0.3 and about 2 percent by weight of a nitrated organic compound containing the nitro group, capable of inhibiting the formation of a heavy phosphate coating while enhancing the formation of a hard, uniformly thin phosphate coating.

10. The composition as claimed in claim 9 wherein the chlorinated hydrocarbon is trichloroethylene.

11. The composition as claimed in claim 9 wherein the nitrated organic compound containing the nitro group is nitrobenzene.

12. A process of phosphate-coating an article made of a metal of the class capable of reacting with phosphoric acid to form a metal phosphate which consists essentially of contacting the article with a composition comprised of a chlorinated hydrocarbon containing a minor proportion of an organic solvent capable of dissolving orthophosphoric acid in the chlorinated hydrocarbon, a phosphatizing proportion of orthophosphoric acid, and an inhibiting proportion of at least 0.01 percent by weight of a nitrated organic compound containing the nitro group, capable of inhibiting the formation of a heavy phosphate coating while enhancing the formation of a hard, uniformly thin, phosphate coating.

13. The process as claimed in claim 12 wherein the chlorinated hydrocarbon is trichloroethylene.

14. The process as claimed in claim 12 wherein the nitrated organic compound containing the nitro group is nitro benzene.

15. A process of phosphate coating an article of a metal of the class capable of reacting with phosphoric acid to form a metal phosphate which consists essentially of contacting the article for up to about twenty minutes at a temperature between about 20 centigrade and about the boiling point with a composition comprised of between about 65 and about 98 percent by weight of a chlorinated hydrocarbon, between about 1.5 and about 25 percent by weight of an alcohol, between about 0.1 and about 6 percent by Weight of orthophosphoric acid, and between about 0.01 and about 6 percent by weight of a nitrated organic compound containing the nitro group, capable of inhibiting the formation of a heavy phosphate coating while enhancing the formation of a hard, uniformly thin phosphate coating.

16. The process as claimed in claim 15 wherein the chlorinated hydrocarbon is trichloroethylene.

17. The process as claimed in claim 15 wherein the nitrated organic compound containing the nitro group is nitro benzene.

18. The process as claimed in claim 15 wherein the alcohol is normal-butyl alcohol.

19. A process of phosphate-coating an article of metal of the class capable of reacting with phosphoric acid to form a metal phosphate which consists essentially of contacting the article for between about 0.5 and about 15 minutes at a temperature of between about 55 and centigrade with a composition comprised of between about and about 97 percent by weight of a chlorinated hydrocarbon, between about 3 and about 15 percent by weight of an alcohol, between about 0.6 and about 2 per cent by weight of orthophosphoric acid, and between about 0.3 and about 2 percent by weight of a nitrated organic compound containing the nitro group, capable of inhibiting the formation of a heavy phosphate coating while enhancing the formation of a hard, uniformly thin phosphate coating.

20. The process as claimed in claim 19 wherein the nitrated organic compound containing the nitro group is nitro benzene.

References Cited by the Examiner UNITED STATES PATENTS 2,295,545 9/42 Clitford et al 1486.l5 2,316,811 4/43 Romig 1486.15 2,336,071 12/43 Clifford et al 148-6.15 2,346,302 4/44 Hays et al. 1486.15 2,515,934 7/50 Verner et a1 1486.15 2,657,156 10/53 Hyams et a1. l486.15 2,702,768 2/55 Hyams et al 1486.l5 2,789,070 4/57 Copelin 1486.15 2,992,146 7/61 Low 1486.15 3,000,977 9/61 Patron et al 260-652.5

FOREIGN PATENTS 1,166,834 6/58 France.

22,743 10/ 10 Great Britain.

RiCHARD D. NEVIUS, Primary Examiner. 

1. A SUBSTANTIALLY WATER-FREE COMPOSITION OF MATTE SUITABLE FOR PHOSPHATIZING METAL CONSISTING ESSENTIALLY OF A CHLORINATED HYDROCARBON CONTAINING A MINOR PROPORTION OF AN ORGANIC SOLVENT CAPABLE OF DISSOLVING ORTHOPHOSPHORIC ACID IN THE CHLORINATED HYDROCARBON, A PHOSPHATIZING PROPORTION OF ORTHOPHOSPHORIC ACID, AND AN INHIBITING PROPORTION OF AT LEAST 0.01 PERCENT BY WEIGHT OF A NITRATED ORGANIC COMPOUND CONTAINING THE NITRO GROUP, CAPABLE OF INHIBITING THE FORMATION OF A HEAVY PHOSPHATE COATING WHILE ENHANCEING THE FORMATIN OF A HARD, UNIFORMLY THIN PHOSPHATE COATING. 